The glucose transport system of the human erythrocyte has been purified. The assay during purification has been based on the binding of the compound cytochalasin B. In the coming year we will investigate the function and structure of the purified transport system. The former will include: a) reconstitution into phospholipid vesicles prepared from specific phospholipids. The rates of sugar transport into these vesicles will be measured. The results will show whether the purified system is fully active as a transporter and will establish the lipid specificity of the system. b) Introduction of the purified system into the plasma membranes of other cell types by membrane fusion procedures. The structural work will include determinations of the subunit structure, amino acid composition, and oligosaccharide composition of the purified transport system. Three other areas of research will be affinity-labeling of the active site of the transporter, development of a new purification method, and determination of the effect of membrane potential upon the kinetics of sugar transport.